A device for controlling a wiper motor was disclosed in German patent DE 33 14 770 C2 and includes an optoelectronic sensor apparatus and a circuit arrangement connected to a drive motor, so that control of the drive motor may be effected in dependence upon the coating present on the windshield.
The device does not, however, include any means for allowing detection of the last sweep process of a wiping cycle which effects a last cleaning of the measuring range of the sensor apparatus. This device may to some extent satisfactorily adapt the wiping cycle frequency automatically to quantitative changes arising during wiper operation in the condition of the coating on the windshield, such as, for example, the degree of dirt accumulation, or the quantity of rain or snow striking the windshield. However, it is not possible satisfactorily to achieve precise automatic adaptation of the wiping cycle frequency to both qualitative and quantitative changes in the condition of the coating on the windshield. Furthermore, with such devices for controlling a windshield wiping system, there arises under certain circumstances an erratic connection and disconnection, or an erratic switching back and forth, between the intermittent and continuous wiping mode of the drive motor. This is, at the very least, distracting to the vehicle operator and difficult to get used to, and may moreover also become a source of unpleasant irritation.